As a coating method in which an excessive amount of a coating liquid is transferred onto a continuously running web (a base material made of a woven fabric or a nonwoven fabric), and then measured to a desired adhesion amount, for example, a Meyer bar coating method, a blade coating method, a roll blade coating method, an air knife coating method, and the like are known.
Of these, the roll blade coating method is widely used for coating of various products, because a liquid having a high density can be applied to form a thin film.
As shown in FIG. 1, the roll blade coating method is a method in which a roll blade 31 is brought into pressure contact with a web 33 whose back surface is supported by a backup roll 32, so as to remove an excessive amount of the coating liquid 34 transferred onto the web 33. Moreover, as shown in FIG. 2, the roll blade 31 is held by a holding member 35. A tubular air containing member 36 configured to press the holding member 35 is arranged in a side of the holding member 35, which side is opposite to a side where the roll blade 31 is held. This causes force which can bring the roll blade 31 into press contact with the web 33.
FIG. 3 shows a conceptual diagram of a cross-section of A-A line in FIG. 1 and a contact pressure between the roll blade 31 and the backup roll 32 corresponding to the width direction position of the cross-section.
The tubular air containing member 36 also applies force to a part of the roll blade 31, which part is not in contact with the web 33 in the width direction. Thus, the contact pressure between the roll blade 31 and the backup roll 32 in the vicinity of both ends of the web 33 may be higher than the contact pressure therebetween at the central part of the web 33 because of unevenness caused by the thickness of the web 33. For this reason, in the conventional roll blade coating, the adhesion amount of the coating liquid in the vicinity of both ends of the web 33 becomes smaller than the adhesion amount thereof at the central part of the web 33, and the film thickness becomes uneven in the width direction.
To solve these problems, for example, in PTL 1 a roll blade coating apparatus is proposed, which can uniformly apply a coating liquid on a web in the width direction by providing a pressure detector which converts pressure of the blade in each position of the width direction into an electric signal.
However, in the roll blade coating apparatus described in PTL 1, pressing force of the web against the roll blade in the width direction cannot be adjusted by mechanical suppress strength, and since the roll blade itself cannot be pressed, the adhesion amount on the web in the width direction is hard to be effectively adjusted.
Moreover, to solve the above-described problems, in PTL 2 a roll blade coating method is proposed, in which an excessive amount of a coating liquid is transferred onto a continuously running web, and then a desired adhesion amount is adjusted with a roll blade so as to coat the web with the coating liquid, and the method includes at least a roll blade pressing step of pressing the roll blade via a holder to a web whose back surface is supported by a backup roll, wherein the roll blade is pressed with inclination of 15° to 45° in a travelling direction of the web with respect to a normal direction of the backup roll, and a tubular air containing chamber arranged to press the roll blade is divided into plural chambers along the width direction of the roll blade, and an air pressure in each of the plural tubular air containing chambers is separately adjusted to obtain uniform pressing force of the roll blade.
However, by the method disclosed in PTL 2, the tube cannot expand to relatively wide in both sides of the divided portions of the tube, and some parts of the tube cannot generate force to press the roll blade. Thus, the tube cannot be finely divided and an apparatus using the method cannot sufficiently function to solve the problems.